Add character class / character exclusion

Author: natecook1000

Sources/_StringProcessing/Regex/DSLList.swift

@@ -330,7 +330,14 @@ extension DSLTree.Atom {
       return a != b
     case (.characterClass(let a), .characterClass(let b)):
       return a.excludes(b)
-    
+    // FIXME: Need to track matching options so we can know if this actually matches
+    case (.characterClass(let a), .char(let b)), (.char(let b), .characterClass(let a)):
+      let s = "\(b)"
+      return a.asRuntimeModel(MatchingOptions()).matches(in: s, at: s.startIndex, limitedBy: s.endIndex) == nil
+    case (.characterClass(let a), .scalar(let b)), (.scalar(let b), .characterClass(let a)):
+      let s = "\(b)"
+      return a.asRuntimeModel(MatchingOptions()).matches(in: s, at: s.startIndex, limitedBy: s.endIndex) == nil
+
     default:
       return false
     }

Tests/RegexTests/OptimizationTests.swift

@@ -31,7 +31,7 @@ import Testing
   }
 
   @available(macOS 9999, *)
-  @Test(arguments: [#/a+b/#, #/a*b/#, #/\w+\s/#, #/(?:a+b|b+a)/#, #/(?:(?:a+b)+b)/#])
+  @Test(arguments: [#/a+b/#, #/a*b/#, #/\w+\s/#, #/(?:a+b|b+a)/#, #/(?:(?:a+b)+b)/#, #/\d+a/#])
   func autoPossessify(pattern: Regex<Substring>) throws {
     var list = DSLList(tree: pattern.program.tree)
     list.autoPossessify()